1. Field Of The Invention
The present invention relates to a descent controller for use on a rope or cable for lowering a person or load in a controlled descent from a higher elevation to a lower elevation, and more particularly to a rope or cable mounted descent control device having a control member including both a deadman brake and a panic brake.
2. Description Of The Prior Art
Descent control devices have been developed, all with the objective of lowering a load from a higher to a lower elevation. These devices have taken many forms and have utilized a variety of elements capable of providing a mechanical advantage together with a braking mechanism. Safety features, such as deadman and panic control features, are equally important, particularly when the device is used for descent, escape, or rescue purposes.
In more recent years, concerns with occupational safety have led to the development of mechanisms which enable a worker to lower himself from an elevated position such as a scaffold, crane, lift truck or platform in the event of an emergency. The equipment is, in many respects, similar to known fire escape devices, mountain climbing equipment, and military equipment.
A descent control device with a deadman brake, in the form of a vertical cylindrical drum or capstan about which a rope is wound and a tapered slot through the drum for receiving and releasably gripping the rope along which descent is made, together with a releasable locking end plate, is shown in U.S. Pat. No. 4,883,146, issued Nov. 28, 1989, to H. M. Varner and E. L. Stech for "DESCENT CONTROL DEVICE WITH DEADMAN BRAKE." The device shown in the patent to Varner et al. includes end plates on each end of a vertical cylindrical drum or capstan with apertures on each end plate through which a rope is threaded. The rope is wound in two or more turns around the drum. The lower plate is provided with an arcuate tapered slot opening into the rope receiving aperture for engaging and binding the rope in order to provide a brake. The rope is mechanically forced into the aperture by a locking end plate rotatably mounted on the capstan below the lower end plate. The locking plate includes an aperture for loosely receiving the rope. A spring rotatably biases the locking plate to releasably and forcibly urge the rope into the narrowed tapered slot in the lower end plate for locking the rope against movement on the capstan. By rotating the locking plate against the force of the spring the rope can be progressively released from the tapered slot.
Tapered slots are ancient and well known in the art of releasably fastening ropes, lines and cables, such as in the nautical field where tapered slots are widely used for engaging and retaining ropes, lines, hawsers and cables. The use of cylindrical capstans for holding and providing a mechanical advantage for tightening ropes is also old and well known. Likewise, a variety of fire escape devices utilizing a rope wound around a cylinder, are old and well known. See, for example, U.S. Pat. No 4,550,801, issued Nov. 5, 1985, to W. E. Forrest for "PERSONAL HIGH RISE EVACUATION APPARATUS"; U.S. Pat. No. 4,311,218, issued Jan. 9, 1982, to L. Steffen for "BRAKING-DEVICE FOR USE WITH CLIMBING LINES"; U.S. Pat. No. 771,251, issued Oct. 4, 1904, to O. Howe for "FIRE ESCAPE"; U.S. Pat. No. 386,237, issued July 17, 1888, to T. Budd for "FIRE ESCAPE"; U.S. Pat. No. 1,115,603, issued Nov. 3, 1914, to J. Smith for "FIRE ESCAPE"; U.S. Pat. No. 536,866, issued Apr. 2, 1895, to C. FitzGerald for "FIRE ESCAPE"; and U.S. Pat. No. 946,588, issued Jan. 18, 1910, to C. Thuemer for "FIRE ESCAPE."